In and relating to machines for forming helically wound lock-seam tubing having multiple wall thickness

ABSTRACT

This invention pertains to a machine for forming helical lock-seam tubing. The machine includes rollers for forming flanges on edges of laterally staggered overlapped strips, a forming head for forming the strips into a helical configuration, rollers for clinching the flanges into locking engagement, reels for supplying the strips, and structure for guiding the strips from the reels to the forming rollers.

This application is a continuation of application Ser. No. 08/244,586,filed Jun. 3, 1994 and now abandoned.

BACKGROUND OF THE INVENTION

This invention concerns improvements in machines for the formation ofhelical lock-seam tubing, and relates more especially to such a machineadapted for the production of such tubing having a multiple wallthickness.

It has hitherto been proposed, see FR-A-2,032,737 and FR-A-2,107,500, toprovide helical lock-seam tubing having a multiple wall thickness.Hitherto, however, the production of a machine capable of forming suchtubing has proposed practical difficulties.

It is accordingly an object of the invention to provide such a machine.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a machine for theformation of helical lock-seam tubing, characterized in that itcomprises means for guiding at least two superposed metal strips inoverlapping relationship successively between a series of formingrollers wherein flanges are formed upon the opposite marginal edges ofthe superposed strips, whilst overlapped upon one another, a pair ofdrive rollers for causing the superposed strips to be drawn through theforming rollers and then advanced towards a helical forming head, andclinching rollers associated with the helical forming head such that theflanges formed at the respective marginal edges of the overlapped metalstrips are clinched into locking engagement with one another to providea helical locked-seam, consecutive helices of which are spaced apart bya distance corresponding to the width of the overlapped metal strips.

Various further optional features may be incorporated in the machine, inaccordance with the invention, in order further to improve the effectivehandling of the overlapped strips.

Thus, according to one aspect of the invention guide rollers betweenwhich the overlapped metal strips are fed to said forming rollers areprovided with radially stepped shoulders so arranged that the stripspassing between the rollers are held with their widths in a staggeredrelationship to one another, the distance of lateral displacement beingso selected that relative displacement of the edges of the strips duringforming of said flanges and clinching of said lock-seam brings thelateral edges of the respective strips to lie in a substantially commonplane. The shoulders of the guide rollers may be adapted to provide forthe location of two overlapping strips or three, or possibly moreoverlapping strips.

According to another aspect of the invention, the drive roller that isarranged for gripping engagement with the exposed surface of that one ofthe overlapping strips that is to be at the exterior surface of thefinished tubing has a knurled or patterned surface. Thus the arrangementof drive rollers is the reverse of that which is utilized in theconventional machine for forming lock-seam tubing.

In accordance with a yet further aspect of the invention, there areprovided at the entry to the helical forming head of the machine, one ormore shaped counter-pressure plates including portions shaped to theradius of curvature of the internal surface of the finished tubing,whereby the overlapping metal strips are held closely in contact withone another during initial bending to the radius of curvature of thehelical forming head.

In order to feed helically coiled strips from supply reels, inoverlapping relationship, to the rollers and the forming head of themachine, independent supply reels carrying the respective strips may bearranged one behind the other in the direction of advance of the striptowards the machine, in such a manner that the strip fed from the reelmore remote from the machine is brought into contact with the nextadjacent strip substantially at a point where the path of the firststrip becomes tangential to a radius of the reel feeding the nextadjacent strip.

In an arrangement where three individual strips are to be fed to thesaid guide rollers of the machine from corresponding supply reels,preferably there is interposed between that supply reel nearest to themachine and said guide rollers, a guide arrangement for maintaining therespective strips in spaced relation, such that the central strip ismaintained substantially coinciding with a guide path tangential to bothsaid rollers, the remaining strips being fed along paths extendingsubstantially symmetrically to the plane of the intermediate strip.Further preferred features and advantages of the arrangement accordingto the invention will become apparent from the following description andthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated by way of example in the accompanyingdrawings in which:

FIG. 1 is a side elevation showing the general arrangement of a machinein accordance with the invention for the formation of helically woundlock-seam tubing of double wall thickness,

FIG. 2 is a similar view of a machine for the formation of tubing havinga three layer wall thickness,

FIG. 3 is a side perspective view illustrating the arrangement of guiderollers, forming rollers, and drive rollers of a machine according toFIG. 1 of the drawings,

FIGS. 4a and 4b are respectively, a transverse cross-sectional view anda side view of guide rollers for use in the formation of lock-seamtubing having two overlapping metal walls with an intermediate layer ofinsulation,

FIGS. 5a and 5b are similar views of guide rollers for three overlappingmetal strips,

FIG. 6 is a diagramatic side elevation illustrating a guide arrangementfor use in feeding three overlapping strips to the machine,

FIG. 7A is a diagramatic side elevation illustrating the provision of aninternal guide plate within the helical forming head of the machine, and

FIG. 7B is a plan view corresponding to FIG. 7A.

DETAILED DESCRIPTION

Referring to FIG. 1 of the drawings, there is shown a generalarrangement of one embodiment of apparatus in accordance with theinvention. The reference numeral 1 illustrates a machine for theformation of helically wound lock-seam tubing, which is of generallyknown type, although various modifications to the known machine will bedescribed in more detail below. Arranged in tandem with the machine 1are two supply reels 2 and 3 that supply metal strip to the machine 1from storage rolls. Thus, a metal strip 4 supplied from the reel 3 isfirst fed into contact with the roll of metal strip stored on reel 2,and, thereafter, the two overlapped metal strips 4 and 5 are fed to themachine 1. As will be described in more detail below, the strips 4 and 5are not fully in register with one another, but are slightly staggeredin the lateral direction.

FIG. 2 shows a similar arrangement wherein strips are fed from threesupply reels 6,7,8, a strip 9 from the reel 8 being advanced intocontact with a strip 10 from reel 7 and then the strips 9 and 10 beingadvanced into contact with a further strip 11 fed from reel 6. At apoint between reel 6 and the machine 1, the three strips 9,10 and 11 areseparated by a guide arrangement 12 described in more detail below, sothat the three strips approach the horizontal guide path of the machine1 in a symmetrical arrangement.

As will be described in more detail below the three strips 9, 10 and 11may comprise either three metal strips, or two metal strips with anintervening layer of insulating material.

As already mentioned above, the machine 1 is of generally known type,but incorporates a number of modifications specifically to enable theformation in this type of machine of a conventional lock-seam at themarginal edges of a plurality of overlapping strips. As indicated inFIG. 3, the portion of the machine concerned with drawing of the metalstrips from the supply reels and subsequent driving of these stripstowards a helical forming head comprises, in generally known manner, apair of nip rollers 20, 21 that are driven from a main motor of themachine, not illustrated, and that pull the metal strips between aseries of three forming rollers 22, 23, 24, before pushing theoverlapping strips into a helical forming head at which flanged edges ofthe strips are brought into engagement with one another and clinchedtogether. The lower roller 21 has a knurled surface for engaging andgripping the surface of the corresponding metal strip.

The three forming rollers 22, 23 and 24 are of generally known type, butare of modified dimension to take account of the fact that the machineis dealing with multiple strips. Thus, assuming that the machine of FIG.3 corresponds to that of FIG. 1 and is forming a tube of double layerthickness from a strip that is of a given lateral width at the time whenit reaches the forming head, the forming roller 24 will be of standardaxial length corresponding to the width of the strip moving to theforming head. However, the forming roller 23 will have its axial lengthincreased for example by 0.75 × the thickness of each metal strip,whereas the forming roller 22 will have its axial length increased by1.5 × the thickness of each metal strip.

In addition, the machine is provided with a pair of guide rollers 25that maintain the overlapping metal strips in laterally staggeredrelationship as they are advanced to the forming rollers 22 to 24.

Thus, as shown in FIGS. 4a and 4b, the upper and lower guide rollers 25aand 25b have staggered recesses defined by end flanges of the rollers,that hold the metal strips in laterally staggered relationship. In FIGS.4a and 4b the rollers are shown as being adapted for the case wherein astrip of insulating material 10 is interposed between two metal strips 9and 11 as illustrated in FIG. 3, but the arrangement will besubstantially identical if the insulating strip is omitted, the radialdepths of the recesses in the rollers 25a and 25b simply being reducedby half the thickness of the insulating strip 10.

FIGS. 5a and 5b show a similar arrangement of the rollers 25 adapted tofeed three overlapping metal strips to the forming rollers, and in thiscase it will be seen that the lateral displacement of the upper andlower strips 9 and 11 is greater than in the case of FIGS. 4 and 4b, dueto the greater thickness of the overlapping strips that are to haveflanges formed thereon by the forming rollers. The difference betweenthe axial lengths of the respective forming rollers 22, 23 and 24 willof course be correspondingly greater. It will be appreciated that sinceall three overlapping strips 9, 10 and 11 are formed with the flangesnecessary for clinching of a helical lock-seam, although the stripsinitially are fed in relatively laterally staggered form as shown inFIG. 5a, the fact that the margins of the strips follow different radiiof curvature as the flanges are bent causes the marginal edges of thestrips to be brought into register, or substantially into register, in acommon plane, as the superposed strips are fed towards the clinchingrollers of the machine. As will be understood by one skilled in the art,the radii of curvature of the corresponding surfaces provided in theforming rollers 22, 23 and 24 and in the external clinching roller willbe matched to the radii of curvature resulting from the requiredformation of the overlapping strips.

As mentioned above, when three overlapping strips are fed to the machine1, there is advantageously provided between the nearest supply reel 6and the machine 1, a guide arrangement 12 for locating the strips indesired symmetrical positions. This arrangement is shown in more detailin FIG. 6, wherein the guide arrangement indicated generally at 12comprises upper and lower guide rollers 30 and 31 that guide the upperand lower strips 9 and 11 as they pass towards the nip of a further pairof guide rollers 32 located at the commencement of the feed path of themachine. Between the rollers 30 and 31 is mounted a guide membercomprising vertical lateral guide plates 33 and upper and lowerhorizontal guide plates 34, 35, between which the insulating strip 10 isguided. The assembly 12 is mounted in fixed relation to the rollers 32by suitable means, not shown, arranged laterally of the paths of thestrips 9, 10 and 11.

Referring to FIGS. 7a and 7b, there are shown diagramatically theconventional forming head 40 of the machine 1 together with upper andlower guide plates 41 and 42 and an internal support roller 43 thatengages the interior of the formed tubing and supports the tubingagainst the pressure of the external clinching roller. All of thesecomponents are provided in the conventionally known machines for theformation of helically wound lock-seam tubing and will be well known toone skilled in the art. In addition, however, there are providedinternal guide plates 44 and 45 of suitable synthetic plastics material,such as POM (polyoxymethylene), that are supported respectively from amounting for the support roller 43 and from a support arm 46 thatprovides additional bracing for the mounting of the support roller 43.POM resin has the required structural properties whilst having a lowcoefficient of friction and being relatively easy to form to therequired shape. As can be seen more clearly from FIG. 7a the guideplates 44 and 45 are shaped to follow the radius of curvature of theforming head 40, as indicated at 47. Thus, as the overlapping metalstrips are urged by the drive rollers 20, 21 into engagement with thecurved surface of the forming head 40 they are supported by the guideplates 44 and 45 during the initial bending to the radius of curvatureof the forming head 40. Thus buckling of the overlapping strips at thispoint is prevented.

It will be appreciated from the above disclosure that the presentinvention accordingly provides novel enhancements of a helical lock-seamforming machine that enables a plurality of overlapping strips of metalor other material to be guided and formed into a helical tube in thesame manner as a single strip. This arrangement accordingly providessignificant advantages over hitherto known proposals for the formationof multi-wall lock-seam tubing, wherein individual handling of separatestrips is necessary, and/or it is necessary to modify the conventionallock-seam of the metal tube.

I claim:
 1. A machine for forming helical lock-seam tubing,comprising:means for receiving a plurality of laterally staggeredoverlapped strips and forming male and female flanges on oppositemarginal edges of said strips, said means for receiving and formingincluding a series of longitudinally adjacent forming rollers; means fordrawing said laterally staggered overlapped strips through said meansfor receiving and forming, said means for drawing including a pair ofdrive rollers spaced one above the other downstream of said means forreceiving and forming; means for forming said laterally staggeredoverlapped strips into a helical configuration while bringing said maleand female flanges into interengagement, said means for formingincluding an external helical forming head located downstream of saidmeans for drawing; means for clinching said male and female flanges intolocking engagement with one another after said male and female flangeshave become interengaged with each other and while said laterallystaggered overlapped strips maintain their helical configuration, saidmeans for clinching including rollers associated with said externalhelical forming head; means for supplying said laterally staggeredoverlapped strips toward said means for receiving and forming, saidmeans for supplying including longitudinally spaced reels each having arespective one of said strips coiled thereabout and each being locatedupstream of said means for receiving and forming, such that a firststrip supplied from a reel upstream of at least one other reel isbrought into a laterally offset contact with a second stripsubstantially at a point where the first strip becomes tangential to andrests upon the second strip while coiled on said at least one otherreel, and then these overlapped strips are supplied towards said meansfor receiving and forming with said first strip on top of said secondstrip and laterally offset relative thereto; and means for guiding saidlaterally staggered overlapped strips to said means for receiving andforming, said means for guiding being located longitudinally betweensaid means for supplying and said means for receiving and forming, andincluding a pair of guide rollers located one above the other, with eachguide roller provided with radially stepped shoulders so that theoverlapped metal strips are passed between said guide rollers withlateral edges of each strip contacting a respective one of saidshoulders such that said strips are maintained in their laterallystaggered overlapping relationship as they are received and formed bysaid means for receiving and forming, wherein said forming rollers ofsaid means for receiving and forming and said guide rollers of saidmeans for guiding are immediately adjacent each other and form a commontrain of rollers.
 2. The machine according to claim 1, wherein the driveroller located above the other drive roller has a knurled surface. 3.The machine according to claim 1, wherein said means for forming furtherincludes at least one internal shaped counterpressure place locatedupstream of said external helical forming head, said at least onecounterpressure plate including portions shaped to the curvature of theinternal surface of the tubing, such that the helically staggeredoverlapped metal strips are held closely in contact with one anotherduring initial shaping thereof by said external helical forming head. 4.The machine according to claim 1, wherein said means for supplyingincludes three reels with metal strips coiled thereabout, and saidmachine further comprises between the downstream most reel and saidmeans for guiding a second guide means for maintaining said strips inspaced relation, such that the central strip is maintained substantiallytangential to both guide rollers and the other strips are maintainedsymmetrically with respect to the central strip.
 5. The machineaccording to claim 1, wherein said second guide means includes a firstpair of spaced apart upper and lower guide rollers, a second pair ofupper and lower guides rollers located downstream from said first pairof spaced apart upper and lower guide rollers, and a guide arrangedbetween said first pair of rollers, whereby the central strip is passedthrough said guide, and the other strips are passed over and under saidfirst pair of rollers, respectively, and then all the strips are passedbetween said second pair of rollers.
 6. The machine according to claim 5wherein said guide includes a pair of upper and lower guide plates and apair of lateral guide plates defining a guide path.
 7. The machineaccording to claim 6, wherein said central strip is an insulatingmaterial and said other strips are metal.